Photoactivatable paint curing device and method

ABSTRACT

A device and method for curing photoactivatable paint coatings. An exemplary device may include a light chamber housing supported by a frame and undercarriage, the wall portions of the light chamber having a peripheral region terminating at a light emission region. A UV light source may be located within the light chamber. A motorized carrier may be provided and configured to controllably index and/or oscillate the UV light source along a travel path within the housing. The light chamber may be located adjacent a target paint cure location on a work piece, with the UV light emission region facing the paint cure location. Once properly located, the UV light source may be indexed and/or oscillated along the travel path to deliver UV light to the target paint cure location so as to cure UV curable paint thereon.

CROSS-REFERENCE TO RELATED APPLICATIONS

As authorized by 35 U.S.C. §119, this application claims priority to andhereby incorporates by reference Canadian Application Serial No.2644766, titled PHOTOACTIVATABLE PAINT CURING DEVICE AND METHOD, filedon Nov. 21, 2008.

BACKGROUND OF THE INVENTIVE FIELD

Conventional manufacturing techniques have seen many improvements inrecent years and painting techniques are no exception. A wide range ofpaint systems are now available, including those formulated with asolvent or water base and electrostatic powder coatings. Solvent orwater based coatings require a curing period following application of apaint layer. Of course, the longer the curing time needed, the greaterthe cost associated with the resulting painting step. Painting steps areusually upstream of several assembly steps. It is all too common in somecases to detect, downstream of the painting step, imperfections in, ordamage to, the painted surface, requiring special remediation steps tocorrect the problem. However, it can be difficult to repair the paintfinish without excessive time spent or collateral damage to neighboringcomponents.

Photoactivatable paints offer significant promise and are typicallycured by UV radiation (otherwise known as UV light). For example, thereis known a dual cure UV system, which utilizes heat and UV radiation andis able to adequately cure any area of a 3D configuration. However,there are numerous limitations to current photoactivatable paintsystems. It is often required to access shadow areas of a 3-Dconfiguration with relatively narrow access points. This is not aproblem for heat curing or likewise dual curing (UV+Heat) since in bothcases air is heated to the required curing temperature and its abilityfor access and thereby heating the paint is utilized to cure paint inboth cases. However, there are two main drawbacks to this methodology.First, dual curing techniques may not be used on assemblies withneighboring heat-sensitive parts. Secondly, the dual curing techniquestend to require longer curing periods and are known to be energyinefficient.

It would be desirable to provide a novel approach to this task.

SUMMARY OF THE GENERAL INVENTIVE CONCEPT

It should be understood that the invention is not limited in itsapplication to the details of construction and the arrangement ofcomponents set forth in the following description or illustrated in thedrawings. The invention is capable of other embodiments and of beingpracticed or of being carried out in various ways. Also, it is to beunderstood that the phraseology and terminology used herein is for thepurpose of description and should not be regarded as limiting. The useof “including,” “comprising,” or “having” and variations thereof hereinis meant to encompass the items listed thereafter and equivalentsthereof as well as additional items. Unless limited otherwise, the terms“connected,” “coupled,” and “mounted,” and variations thereof herein areused broadly and encompass direct and indirect connections, couplings,and mountings. In addition, the terms “connected” and “coupled” andvariations thereof are not restricted to physical or mechanicalconnections or couplings. Furthermore, and as described in subsequentparagraphs, the specific mechanical, electrical or other configurationsillustrated in the drawings are intended to exemplify embodiments of theinvention. However, other alternative mechanical, electrical or otherconfigurations are possible which are considered to be within theteachings of the instant disclosure. Furthermore, unless otherwiseindicated, the term “or” is to be considered inclusive.

In one exemplary embodiment, there is provided a device for curingphotoactivatable paint coatings. The device has an undercarriage, aframe positioned on the undercarriage, a housing supported on the frame,the housing having a back wall and a plurality of side wall portionsextending therefrom to form a light chamber, each side wall portionhaving a peripheral region terminating at a UV light emission region, aUV light source contained within the light chamber, a motorized carrierto support the UV light source in the light chamber, the motorizedcarrier configured to index and/or oscillate the UV light source along atravel path within the housing, and a controller for controlling themotorized carrier, the frame and undercarriage being further arranged tolocate the light chamber adjacent a target paint cure location on a workpiece with the UV light emission region facing the paint cure location,the controller being operable to activate the UV light source and toinitiate the motorized carrier to index and/or oscillate the UV lightsource along the travel path to deliver UV light to the target paintcure location for curing UV curable paint thereon.

In another exemplary embodiment, the motorized carrier includes a firstlinear actuator operating along a first axis and a second actuatoroperating along a second axis, and in one example the first and secondaxes are perpendicular, though they may be non-perpendicular if desired.

In another exemplary embodiment, the UV light source includes at leastone bulb having a diameter of about 20 mm to about 40 mm, and in oneexample has a diameter of 25 mm.

In another exemplary embodiment, the light chamber has lateraldimensions of about 75 mm to about 100 mm and a depth of about 50 mm toabout 100 mm. In one example, the light chamber has lateral dimensionsof about 85 mm and about 60 mm respectively, and a depth of about 93 mm.

In another exemplary embodiment, the target paint cure location haslateral dimensions ranging from about 50 mm to about 300 mm, and fromabout 50 mm to about 300 mm respectively. In one example, the targetpaint cure location has dimensions of about 90 mm and about 60 mmrespectively.

In another exemplary embodiment, the motorized carrier includes a firsttravel cylinder configured to displace the UV light source along thetravel path between opposed ends of the light chamber, and a secondindexing cylinder to cause a synchronized incremental shift of the path.The boundaries of the travel path may, in some cases, be identified bylimit switch units, and a reversing unit may be employed for reversingthe travel of the first travel cylinder following activation of acorresponding limit switch unit.

In another exemplary embodiment, the device employs a bulb in the formof a fluorescent UV lamp, emitting at a wavelength from about 200 toabout 400 nanometers. More particularly, the fluorescent UV lamp mayemit at a wavelength from about 320 nm to about 390 nm.

In alternative embodiments, the UV light source may include one or moreLED, fluorescent and/or incandescent lamps.

In another exemplary embodiment, there is provided a device for curingphotoactivatable paint coatings, comprising a housing, a radiationsource located in the housing, the housing having opposed firstboundaries to define a first pair of boundaries and a pair of secondboundaries, the first and second boundaries defining a radiationpassage, the radiation source configured to emit radiation through theradiation passage to cure a photoativatable paint coating at a targetlocation located adjacent the radiation passage; a motorized supportsupporting the radiation source, the motorized support configured in afirst phase to displace the radiation source along a first path betweenthe first boundaries, the motorized support configured in a second phaseto index the first path laterally along a second path between the secondboundaries.

In another exemplary embodiment, the motorized support is configured torepeat the first and second phases. In one example, the motorizedsupport is further configured to reverse the direction of the radiationsource when it reaches a limit adjacent a corresponding first boundary.The motorized support may be further configured to oscillate theradiation source along the first path between the first boundaries andto index the first path between oscillations.

In another exemplary embodiment, there is provided a method for curing aphotoactivatable paint coating on a work piece, comprising providing aradiation source within a housing, the housing having opposed wallportions to define a first pair of boundaries and a pair of secondboundaries, the first and second boundaries defining a radiation passagetherebetween, configuring the radiation source to emit radiation throughthe radiation passage, positioning the housing a sufficient distance toa photoativatable paint coating at a target location for the radiationsource to activate the paint coating, displacing the radiation source ina first phase along a first path between the first boundaries and, in asecond phase, indexing the first path laterally along a second pathbetween the second boundaries.

Another exemplary embodiment provides a work piece comprising a curedcoating according to the above method.

In still another exemplary embodiment, there is provided a device forcuring photoactivatable paint coatings, comprising a curing radiationsource configured to emit radiation sufficient to cure aphotoactivatable paint coating at a target location when the radiationsource is located at a source location operably spaced from the targetlocation for curing the photoactivatable paint coating thereon, amotorized support for supporting the curing radiation source at thesource location, the motorized support configured to advance the curingradiation source along a travel path, the motorized support furtherconfigured to cycle the curing radiation source along the travel pathbetween a first position and a second position in order to vary overtime the angle of attack of the radiation emitted from the curingradiation source on the photoactivatable paint coating at the targetlocation.

A further embodiment comprises a housing to provide an operating region,a support for the housing, the support configured to maintain thehousing stationary during cycling of the light source along the travelpath. First and second actuators may be provided for moving theradiation source along the travel path relative to two correspondingaxes.

An embodiment further comprises a support structure for supporting thefirst and second actuators, the travel path tracing a theoreticalsurface relative to the target surface, the support structure providinglateral and/or vertical adjustment of the theoretical surface relativeto the target location. The theoretical surface may be planar or nonplanar.

An embodiment provides the motorized support further as a robot arm withthe radiation support mounted on a remote end thereof. In this case, theremote end may additionally support a pair of linear actuators, thelinear actuators supporting the radiation source.

In still another embodiment, there is provided a method for curingphotoactivatable paint coatings, comprising providing a curing radiationsource, orienting the curing radiation source at a source locationrelative to a target surface, spacing the source location from thetarget location, in order for the curing radiation source to emitradiation sufficient to cure a photoactivatable paint coating at thetarget location, establishing an operating region surrounding the targetlocation, the curing radiation source having an angle of attack relativeto the target location, cycling the curing radiation source along atravel path which is confined within an operating region between a firstposition and a second position in order to cycle changes in the angle ofattack.

Another exemplary embodiment further comprises providing the curingradiation source within a housing with an inner region corresponding tothe operating region with an opening, orienting the housing so that theopening is adjacent the target surface, and maintaining the housingsubstantially stationary relative to the target location while cyclingcuring radiation source along the travel path within the housing. Ahousing may also be provided to confine the operating region, a supportfor the housing, the support configured to maintain the housingstationary during cycling of the light source along the travel path.

In yet another exemplary embodiment, there is provided a method forcuring photoactivatable paint coatings in confined regions of a vehiclebody, comprising providing a curing radiation source, orienting thecuring radiation source at a source location in a confined region in avehicle body relative to a target surface in the confined region,spacing the source location from the target location, in order for thecuring radiation source to emit radiation sufficient to cure aphotoactivatable paint coating at the target location, establishing anoperating region surrounding the target location, the curing radiationsource having an angle of attack relative to the target location,cycling the curing radiation source along a travel path within anoperating region between a first position and a second position in orderto cycle changes in the angle of attack.

A further exemplary embodiment includes locating the curing radiationsource within a housing with an inner region corresponding to theoperating region, the housing having an opening and being ofsufficiently compact configuration to be located within the confinedregion, the housing further including an opening, orienting the housingso that the opening is adjacent the target surface, and maintaining thehousing substantially stationary relative to the target location whilecycling the curing radiation source along the travel path within thehousing. In one example, the support is configured to maintain thehousing stationary during cycling of the light source along the travelpath.

Another exemplary embodiment provides a vehicle comprising a cured paintcoating according to the above method.

BRIEF DESCRIPTION OF THE DRAWINGS

Several exemplary embodiments of the present invention will be provided,by way of examples only, with reference to the appended drawings,wherein:

FIG. 1 is a side view of a device for curing photoactivatable paintcoatings;

FIG. 2 is another side view of the device of FIG. 1 in an operativeconfiguration;

FIG. 2 a is another side view of the device in another operativeconfiguration;

FIGS. 3 and 4 are plan views of a housing portion of the device of FIG.1 in alternative operational configurations;

FIGS. 5 a and 5 b are schematic views showing a prior art paint curingmethod;

FIGS. 6 a and 6 b are schematic views showing a comparative paint curingmethod using the device of FIG. 1;

FIGS. 7 a and 7 b are schematic views showing successive operationalpositions in a method of one embodiment of the present invention;

FIGS. 8 and 9 are schematic plan and side views, respectively of anothercuring device;

FIG. 10 is a perspective view of an operational aspect of a methodaccording to one embodiment of the present invention;

FIG. 11 is a schematic plan view of another curing device;

FIG. 12 is a plot of Irradiance for a curing method;

FIG. 13 is a schematic representations of a sample cure analysis of aprior art curing technique; and

FIG. 14 is a schematic representation of a sample cure analysis of acuring technique according to one embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Referring to the figures, there is provided a UV curing device 10 havingan undercarriage 12 with a frame 14 positioned on the undercarriage 12.A housing 16 is supported on the frame 14 and has a back wall portion 18and a plurality of side wall portions 20 extending therefrom to form alight chamber 22. The side wall portions 20 provide a peripheral regionterminating at a UV light emission region 24. A UV light source 30 iscontained within the light chamber 22. The frame has an arm 26 made upof a number of articulated arm portions 26 a, joined at respectivejoints shown at 26 b, allowing the arm to be adjusted to bring thehousing 16 into position relative to a target paint cure location 40 ascan be seen in FIGS. 2 and 2 a. The arm 26 extends outwardly from a post28.

As shown in FIG. 3, a motorized carrier 32 supports the UV light source30 in the light chamber 22 and is configured to index and/or oscillatethe UV light source along a light path 34. Referring to FIG. 1, acontroller 36 is also provided for controlling the motorized carrier 32.The frame 14 and undercarriage 12 are further arranged to locate thelight chamber 22 adjacent the target paint cure location 40 (FIG. 2) ona work piece with the UV light emission region 24 facing the targetpaint cure location 40. As shown in FIG. 2, the target paint curelocation is illustrated to be on an exterior surface of a vehicle body.However, the device 10 may be particularly useful, as shown in FIG. 2 a,to be deployed in confined spaces within, or near, a work space, such aswithin an inner region of a vehicle body, for target paint curelocations which are otherwise difficult to reach in order to providesufficient direct UV radiation for effective curing. In this lattercase, the housing 16 shown in FIG. 2 a is proportionally smaller thanthe housing 16 of FIG. 2, when compared with the overall size of thevehicle body. Thus, in the example of FIG. 2 a, the device 10 isparticularly useful for repairing damaged paint coatings, especially atlocations which are difficult to reach using traditional UV radiationtechniques, such as in fender wells, engine, passenger or trunkcompartments, for instance, within the vehicle body.

The controller 36 is operable to activate the UV light source 30 and toinitiate the motorized carrier 32 to index and/or oscillate the UV lightsource 30 along the light path 34 to deliver UV light to the targetpaint cure location 40 for curing UV curable paint thereon. The speed atwhich the motorized carrier 32 displaces the UV light source will dependon a number of factors, including the power of the UV light source, theproximity of the UV light source to the target location, thephotoactivation rate of the paint and the like. That being said, in oneexample, the speed of travel of the UV light source along the light path34 may, for instance, range from 5 cm per second to 50 cm per second,while the housing 16 remains stationary, though other speeds may also beapplicable in some cases. In one example, the speed of travel is set at10 cm per second and has been shown to yield favorable results.

Referring to FIG. 3, the motorized carrier includes a first linearactuator 42 operating along a first axis A which is parallel to thelight path 34 and a second linear actuator 44 operating along a secondaxis B which is transverse to the first axis A. In this case, the firstand second axes A and B are perpendicular, though other arrangements ofone or more axes may be used as desired.

The UV light source 30, in this example, may be provided with at leastone bulb having a diameter of 20 to 40 mm, and more particularly adiameter of about 25 mm. For a UV light source of this dimensionalrange, the light chamber 22 may be provided with lateral dimensions of75 mm to 100 mm and a depth of 50 to 100 mm. More particularly, thelight chamber 22 may be found to work in a vehicle assembly environmentwith lateral dimensions of between 85 mm and 60 mm respectively and adepth of 93 mm. With these dimensions, as seen in FIG. 6 a, a targetlocation 40 having lateral dimensions, such as dimension “a” rangingfrom 50 mm to 300 mm and dimension “b” ranging from 50 mm to 300 mm, mayyield desirable results with sufficient curing. The target location 40may, within this range, have dimensions of 90 mm and 60 mm respectively,making the device particularly useful for paint curing on target paintcure locations in confined locations within a work piece, for instance.That being said, other dimensions may also be found to yield usefulresults.

The light source 30 is provided by a bulb which, in one example, is afluorescent lamp, emitting at a wavelength from 200 to 400 nanometers,more particularly from 320 to 390 nm. However, the light source mayinclude one or more LED, fluorescent and/or incandescent lamps. In oneexample, the device utilizes a Medium to Low pressure microwave lamp,commercially available from FUSION under the model name PC-1 to generatea reasonably consistent UV radiation intensity output over time toachieve a reasonably consistent UV curing process. Testing has showndevice 10 to be useful in curing thiol-based UV curable paintscommercially available from AKZO NOBEL. The device 10, in most cases,may avoid the need to remove heat sensitive parts for high intensity UVcuring of a UV coating to obtain useful properties and performance. Theexemplary light source 30 has been demonstrated not to heat the targetbaking area above 35 degrees Celsius over the duration (zero to 10minutes) of a paint cure operation (at a distance of 1 mm to 30 mm fromthe target paint cure location). This example may be useful to curepaint on substrates having relatively larger and/or contoured surfacesas well as to eliminate, in some cases, the need to remove heatsensitive parts when the curing device and process as described isapplied to a region on an assembled vehicle, thus giving rise to arelatively rapid, energy efficient process.

The device 10, in some cases, is capable of emitting a wider spectraloutput without raising the substrate temperature above 35 degreesCelsius. The housing may be selected to be relatively compact, to allowample access to relatively narrow spaces, as shown in FIG. 2 a, whichwere previously unable to receive direct UV radiation, more particularlydirect oscillating UV radiation. The device 10 thus provides a UV paintcuring system when combined with a suitable UV activatable paintcomposition.

While the device 10, in this particular example, makes use of a singlelamp, it will be understood that a device of the present invention maysimilarly be operated with more than one lamp as desired, such as with abank of UV lamps, provided that the bank of UV lamps is moving, forexample in an oscillating or repeating manner, along a light pathrelative to the vehicle and operatively positioned relative to thetarget surface. A device of the present invention may also similarly beoperated with a lamp(s) of different size(s).

Thus, in one example configuration, the device enables a UV light sourceto be located inside a housing with the provision of an indexable trackto allow for oscillating of the light relative to a repair site, whilethe housing remains stationary. The device may involve two air cylinders(such as an SMC programmable brake cylinder—index cylinder and a SMCpneumatic cylinder—travel cylinder) in a single configuration toeffectively move the UV lamp to cure relatively larger areas (forexample 300 mm×300 mm). The brake cylinder (index cylinder) may beutilized to enable incremental travel along the axis B (for example atravel of about 50 mm) with capabilities to be programmed to muchsmaller increments (for example a travel in the order of about 1 mm ormore). The lamp may then be displaced to ensure uniform and adequate UVlight exposure of the target location. This configuration thus enablespre programming of travel length in intervals, for example ranging fromabout 10 mm to about 50 mm. The SMC pneumatic cylinder (travel cylinder)enables motion along the axis B. The travel distance may be set by usingposition adjustable limit switches thus capable of traveling between arange of required lengths, for instance a range of 100 to 300 mm, thoughother lengths may also be appropriate depending on the dimensions of thetarget location and the operating parameters of the device. One cyclemay thus include one increment along axis A (for example 50 mm) and oneincrement along axis B (for example 300 mm). The configuration completesa set or predetermined number of cycles (for example six cycles) to curea target surface (for instance having a square area of 300 mm×300 mm.

Thus, in one example, the motorized carrier thus includes a first travelcylinder configured to displace the light source along a travel pathbetween opposed ends of the light chamber, and a second indexingcylinder to cause a synchronized incremental shift of the path. Theboundaries of the travel path are identified by limit switch units,which may be position-adjustable as desired. A reversing unit may alsobe provided for reversing the travel of the first travel cylinderfollowing activation of a corresponding limit switch unit.

While the device 10 is described as a UV device, capable of emitting UVradiation for curing a UV curable paint coating, there may be otherapplications using other photoactivatable paint coatings in which thedevice may be employed with another radiation source other than a UVradiation source, provided that the emission wavelength from theradiation source is complementary for curing the coating in question.

A particular feature of the device 10 is the motion imparted on thelight source which enhances the paint curing function by progressivelychanging the physical location of the radiation source relative to thetarget location. In one example this progressive change in the physicallocation of the radiation source occurs at a substantially regulardisplacement rate or speed, but may also occur at a substantiallyirregular rate in other examples. While not intending to be bound bytheory, it is believed that the changing or repositioning of the UVlight source during curing achieves more thorough curing since the UVrays are able to reach different depths of the coating at differentangles of attack depending on the distance between UV source and thetarget surface. This is seen in FIGS. 7 a and 7 b, where the radiationsource 30′ moves along path 34, above the target surface 46. It can beseen that the angle of attack changes from one location (θa) to anotherlocation (θb).

A further factor resides in the fact that the action of curing is lightintensity dependent, while the intensity of light is a function of thedistance between the UV source and the target surface, resulting in morecomplete and penetrating exposure of the molecular structure of theuncured coating on the target surface to the radiation causing curing tooccur more effectively at deeper levels of the paint at the targetsurface. Both the UV light source and the resin composite cooperate toprovide adequate polymerization (curing) of a UV curable coating. Thecoating composition, light intensity and wavelength are contributingfactors. A curing light's intensity output depends on the type of lightsource, condition of the light source and optical filters and lightguides, as well as voltage, and power; and the distance of the lightfrom the coated surface. The “total energy” (that is, the product oflight intensity and exposure time) may be seen to influence themechanical properties of the cured coating surface. The distance of thecuring light source from the coating surface may also be important. Ifthe amount of light reaching the coating surface is reduced, the depthof cure may be decreased. The amount of light reaching the lower layersof the coating surface may be diminished as the distance is increased.Light intensity may also be reduced as distance increases for differenttypes of lamps (tungsten, halogen, LED and UV curing lamps).

Thus, in some cases, the reciprocal, oscillating or regular motion ofthe lamp is believed to provide a more uniform intensity over thecoating on a target surface, thus enabling a more uniform cure both onthe surface of the coating and throughout the depth of the coating, soas to provide an effective and relatively consistent cure of the coatingon the target surface while requiring relatively less energy to do so,in some cases.

While the device 10 utilizes a motorized carrier which displaces a UVradiation source along a linear path, it may also be configured todisplace the UV radiation source along a non-linear path, such as forexample a circular path, within the housing.

The housing is provided with inner surfaces which are able to reflectscattered UV radiation to the work piece and add to an improvedradiation delivery. While the housing is useful in some configurations,the housing may not be required in all cases. Similar results may beachieved by mounting one or more UV lamps for similar oscillatory orrepeating motion to pass the UV lamps and hence deliver direct UVradiation along a path established on the target surface so that such UVlight is delivered directly to substantially the entire target surfaceat a speed selected according to one or more of the intensity of the UVlight, the distance of the light to the target surface and the cure rateof the photoactivatable coating on or in the target surface.

Referring to FIG. 8, another device is provided at 50 which has amotorized support which supports a micro curing radiation source at thesource location 52 and which is configured to advance the curingradiation source along a micro travel path as shown at 54. A motorizedsupport is configured to cycle the curing radiation source along thetravel path shown at 54 between a first position shown at 30′ and asecond position 30″ as shown in FIG. 6 a in order to cycle changes inthe angle of attack of the radiation emitted from the curing radiationsource on an individual location on the photoactivatable paint coatingat the target location. For example, as can be seen by FIGS. 7 a and 7b, the angle changes from θa to θb as the radiation source moves alongthe path between two locations.

In this case, the radiation source is carried by first and secondactuators shown at 56, 58 for moving the radiation source along thetravel path relative to two corresponding axes x and y. The actuatorsare in turn supported by a support structure 60 including a pair oflongitudinal track portions 62 and a pair of lateral track portions 64.An undercarriage structure 66 is movably supported by the track portionsunder the action of one or more drive units, for example as shownschematically at 68, 70. A pair of vertical drive units is also providedschematically at 74, allowing for vertical adjustments, as shown in FIG.9.

In this case, the travel path may be considered to trace a theoreticalsurface 72 relative to the target surface as shown in FIG. 10. Thesupport structure 60 thus provides lateral and/or vertical adjustment ofthe theoretical surface 70 relative to the target location 46. In oneoperating mode, the theoretical surface 70 is planar, by the fixedelevations of the linear actuators, but may be angled relative to thetarget surface by coordinated actuation of the actuators 56, 58 anddrive units 68, 70 and 74. If desired, the drive units 68, 70 and 74 maybe used with the actuators 56, 58 or in place of the actuators 56, 58 toprovide a macro travel path shown in dashed lines at 74. In this case,the micro or macro travel paths may be employed singly or together.

While the theoretical surface is planar in the above example, thetheoretical surface may be non-horizontal and/or non-planar if desired,by implementing a combination of lateral and vertical drive units. Inyet another example, the motorized support is provided by way of a robotarm 76 as shown in FIG. 11. In this case, the radiation support ismounted on a remote end thereof. It can be seen that the remote endsupports a pair of linear actuators, which in turn support the radiationsource. Alternatively, the radiation source may be held directly by theremote end without the actuators, so that the robot may be programmed tofollow along the path.

EXAMPLE

A trial was carried out in which test samples forming a target surface46 in the form of a 5 cm×15 cm coated section (coated with BASF VP 126UV Primer) was cured using a prior art configuration comprising anarrangement of multiple lamps (three lamps of models FUSION PC-1 inseries and held stationary during curing). This configuration can beseen in figures 5 a and 5 b, where the UV source is shown in dashedlines at Ps and a central curing zone is shown at Pz.

A comparative test was also carried out using the configuration of FIG.1 with a single FUSION PC-1 lamp model. As shown schematically at FIGS.6 a and 6 b, the lamp of this configuration is located within a housingso as to result in an operating region 16 a. For the trial using theconfiguration of FIG. 1, the UV source 30 was oscillated so thatsubstantially the entire target surface 46 was exposed to direct UVradiation from the lamp. In other words, the UV source is oscillated,within the operating region to pass over the entire target surface 46 byadjusting the distances travelled along the A and B axes to exceed thesurface area of the target surface. For the trial using the prior artconfiguration, the three UV sources (or lamps) Ps were centrally alignedwith the target surface and held stationary. The distance of the UVsources to the target location and the time duration of UV radiationexposure was the same in both trial configurations. The UV sources wereheld 5 cm from the test panel for a duration of 120 seconds during bothtrials.

In the case of the prior art configuration, two regions of cure arefound. The central region Pz of the target surface which is directly infront of the three stationary lamps showed effective UV curing.Surrounding the central region of the target surface was a peripheralregion Pp which demonstrated less UV curing, the degree of curinggenerally reducing with a tail off (or reduction of UV light intensity)in the periphery or edges of the three stationary UV light sources. UVlight intensity was measured with an EIT UV POWER PUCK II S/N 11104, adevice commonly used for measuring UV output, to generate an EIT UVpower map of each case in the form of a trace along an X axis relativeto the focal point of the lamp. FIG. 12 illustrates an exemplified powermap, showing the Irradiance at each location along the trace with the 0position being that which is directly below. FIG. 12 also illustrates across sectional view of the exemplified UV lamp with a focal distance of5 cm and identifying the x-axis running below the lamp opening.

Moreover, the central region Pz, demonstrated a cure level of as low as50 to 60 percent depending on the distance from the focal point of thelamps. In this example, a Fourier Transform Infrared Spectroscopy (FTIR)method was employed to confirm cure of a UV curable coating. This wasdone by correlating acrylate conversion as a function of percentage ofUV curing, corresponding to the loss of unsaturated acrylate groups,according to techniques established by Lazzara (1984) to determine thedegree of polymerization. (Lazzara, M. G., “Techniques to MeasureMelamine/Polyol reactions in a film,” Journal of Coatings Technology,56, No. 710, 19 (1984)).

In each case, after a subject panel was cured, six samples were takenfrom the center, and 1 cm, 2 cm and 2.5 cm from the center of the paneloutwards in both directions. A small sample was removed from each area.The FTIR method was then carried out on each sample to determine theactual resin conversion to determine the cure. Each sample was depositedon quartz substrates for FTIR analysis.

The thickness of the coating layers was determined using a RUDOLPH AUTOEL II ELLIPSOMETER. The coating thickness was measured at 40 micrometers±2 micrometers for all samples.

The chemical changes after UV curing of the coating samples weredetermined by FTIR spectra obtained for each sample, using a PERKINELMER FTIR spectrophotometer under the trade name “PARAGON 1000”,according to and based on acrylate conversion. The consumption of alkenebonds (that is the (C═C) group in the coating) as a result of curingreaction was calculated in terms of the percentage reduction of C═C bondat 1665 cm-1. As polymerization progresses, the amount of unsaturatedalkene bonds (C═C) is reduced. (Ryczkowski, J., Rayss, J. VibrationalSpectroscopy, 22 (2000)).

Using the FTIR method, the prior art configuration trial was shown toachieve a 98% cure level for the central region Pz of the target surfacethat was directly aligned with or under the focal point of the lamp. Ascan be seen in FIG. 13 and in Table 1, below, samples 3 and 4, whichrepresent the central location of the panel, showed 98% cure.

The configuration using the device of FIG. 1, as shown in FIGS. 6 a and6 b, resulted in significantly improved through-cure when compared tothe prior art configuration, with a 32 percent improvement in cure (thatis, in resin conversion following UV irradiation) compared to the priorart procedure. The configuration using the device of FIG. 1 showed asignificantly more uniform cure of 98%±2% over the entire targetsurface. The present method thus demonstrates a relatively moreconsistent cure over a relatively larger target surface, using a thirdless UV radiation, and thereby resulting in a potential savings inenergy.

TABLE 1 CURE CONDITION OF THE COATING (Resin conversion) CONTROL TESTSAMPLE Surface Through Surface Through ID LOCATION cure cure cure cure 12 cm from the 67% 51% 98% 98% center 2 1 cm from the 77% 68% 98% 98%center 3 Center 98% 98% 98% 98% 4 Center 98% 98% 98% 98% 5 1 cm from the67% 51% 98% 98% center 6 2 cm from the 77% 68% 98% 98% center

The entire subject matter of each of the references described herein,including the following prior art references is incorporated herein byreference.

-   [1] Friedman J. Variability of lamp characteristics in dental curing    lights. J Esthet Dent 1989; 1(6): 189-90.-   [2] Dugan W. T., Hartleb J. H. Influence of a gluteraldehyde    disinfecting solution on curing light effectiveness. Gen Dent 1989;    37(1): 40-3-   [3] Fan P. L., Wozniak W. T., Reyes W. D., Stanford J. W. Iradiance    of visible light curing units and voltage variation effects. J Am    Dent Assoc 1987, 115: 442-5.-   [4] Felix C. A., Price R. B. The effect of distance from light    source on light intensity from curing lights. J Adhes Dent 2003;    5(4): 283-91.-   [5] Miyazaki M, Ohida, Y, Moore B. K., Onose, H. Effect of light    exposure on fracture toughness and flexural strength of light cured    composites. Dent Mater 1996; 12(6): 328-32.-   [6] Suh B. I., Cripe C. A., Cincionne F. Shrinkage stress relaxation    using pulsed curing. J Dent Res 1998; 77:280 (Abstr No. 1394).-   [7] Price R. B., Derand T., Sedaous M., Andreou P., Loney R. W.    Effect of distance on the power density from two light guides. J    Esthet Dent 2000; 12(6): 320-7-   [8] Meyer G. R., Ernst C., Willershausen B. Decrease in power out    put of new light-emitting diode (LED) curing devices with increasing    distance to filling surface. J Adhes Dent 2002; 4(3): 197-204.-   [9] Prati C., Chersoni S., Montebugnoli L., Montanari G. Effect of    air, dentin and resin based composite thickness on light intensity    reduction. Am J Dent 1999; 12(5): 231-4.-   [10] Moseley H, Strang R., Stephen K. W. An assessment of visible    light polymerizing sources. J Oral Rehabil 1986; 13: 215-24.-   [11] Sakaguchi R. L., Douglas W. H., Peters M. C. Curing light    performance and polymerization of composite restorative materials.

While the present invention has been described based on severalexemplary embodiments, the invention is not so limited. To the contrary,the invention is intended to cover various modifications and equivalentarrangements included within the spirit and scope of the appendedclaims. The scope of the following claims is to be accorded the broadestinterpretation so as to encompass all such modifications and equivalentstructures and functions.

1. A device for curing photoactivatable paint coatings, comprising: anundercarriage; a frame positioned on the undercarriage; a housingsupported on the frame, the housing having a back wall and a pluralityof side wall portions extending therefrom to form a light chamber, eachside wall portion having a peripheral region terminating at a UV lightemission region; a UV light source contained within the light chamber; amotorized carrier to support the UV light source in the light chamber,the motorized carrier including a first travel cylinder configured todisplace the UV light source along a travel path between opposed ends ofthe light chamber so as to index and/or oscillate the UV light sourcealong the travel path within the housing; a controller for controllingthe motorized carrier within boundaries of the travel path, theboundaries being identified by limit switch units; and a reversing unitincluded with the motorized carrier for reversing the travel of thefirst travel cylinder following activation of a corresponding limitswitch unit; wherein the frame and undercarriage are further arranged tolocate the light chamber adjacent a target paint cure location on a workpiece, with the UV light emission region facing the paint cure location;and wherein the controller is operable to activate the UV light sourceand to initiate the motorized carrier to index and/or oscillate the UVlight source along the travel path to deliver UV light to the targetpaint cure location for curing UV curable paint thereon.
 2. The deviceof claim 1, wherein the motorized carrier includes a first linearactuator operating along a first axis and a second actuator operatingalong a second axis.
 3. The device of claim 2, wherein the first andsecond axes are perpendicular.
 4. The device of claim 1, wherein the UVlight source includes at least one bulb having a diameter of betweenabout 20 to about 40 mm.
 5. The device of claim 4, wherein the bulb hasa diameter of about 25 mm.
 6. The device of claim 5, wherein the lightchamber has lateral dimensions of between about 75 mm to about 100 mmand a depth of between about 50 to about 100 mm.
 7. The device of claim6, wherein the light chamber has lateral dimensions of about 85 mm andabout 60 mm, respectively, and a depth of about 93 mm.
 8. The device ofclaim 7, wherein the target paint cure location has lateral dimensionsranging from about 50 mm to about 300 mm and from about 50 mm to about300 mm respectively.
 9. The device of claim 7, wherein the target paintcure location has dimensions of about 90 mm and about 60 mm,respectively.
 10. The device of claim 1, wherein the motorized carrierincludes a second indexing cylinder to cause a synchronized incrementalshift of the path.
 11. The device of claim 1, wherein the light sourceis a fluorescent UV lamp emitting at a wavelength between about 200 toabout 400 nanometers.
 12. The device of claim 1, wherein the fluorescentUV lamp emits at a wavelength between about 320 to about 390 nm.
 13. Thedevice of claim 1, wherein the UV light source includes one or more LED,fluorescent and/or incandescent lamps.
 14. A device for curingphotoactivatable paint coatings, comprising: a housing, the housinghaving opposed first boundaries to define a pair of first boundaries anda pair of second boundaries, the first and second boundaries beingidentified by limit switch units and defining a radiation passage; aradiation source located in the housing, the radiation source configuredto emit radiation through the radiation passage to cure aphotoativatable paint coating at a target location located adjacent theradiation passage; and a motorized support supporting the radiationsource, the motorized support configured in a first phase to displacethe radiation source along a first path between the first boundaries andin a second phase to index the first path laterally along a second pathbetween the second boundaries, the motorized support including areversing unit for reversing the displacement of the radiation sourcealong the first path and/or the second path following activation of acorresponding limit switch unit.
 15. The device of claim 14, wherein themotorized support is configured to repeat the first and second phases.16. The device of claim 15, wherein the motorized support is configuredto oscillate the radiation source along the first path between the firstboundaries and to index the first path between oscillations.
 17. Amethod for curing a photoactivatable paint coating on a work piece,comprising: providing a motorized support for supporting a radiationsource within a housing, the housing having opposed wall portions thatdefine a pair of first boundaries and a pair of second boundaries, thefirst and second boundaries being identified by limit switch units anddefining a radiation passage therebetween; configuring the radiationsource to emit radiation through the radiation passage; positioning thehousing a sufficient distance from a photoactivatable paint coating at atarget location for the radiation source to activate the paint coating;reversibly displacing the radiation source by way of the motorizedsupport in a first phase along a first path between the first boundariesand, in a second phase, indexing the first path laterally along a secondpath between the second boundaries; wherein the motorized supportincludes a reversing unit for reversing the displacement of theradiation source along the first path and/or the second path followingactivation of a corresponding limit switch unit.
 18. A method for curingphotoactivatable paint coatings in confined regions of a vehicle body,comprising: providing a curing radiation source supported on a motorizecarrier; orienting the curing radiation source at a source location in aconfined region in a vehicle body relative to a target surface in theconfined region; spacing the source location from the target location;in order for the curing radiation source to emit radiation sufficient tocure a photoactivatable paint coating at the target location,establishing an operating region surrounding the target location, thecuring radiation source having an angle of attack relative to the targetlocation; and cycling the curing radiation source, by way of themotorized carrier including a reversing unit, along a travel path withinthe operating region having boundaries defined by limit switch unitsbetween a first position and a second position in order to cycle changesin the angle of attack following activation of a corresponding limitswitch unit.
 19. The method of claim 18, further comprising locating thecuring radiation source within a housing with an inner regioncorresponding to the operating region, the housing having an openingwith a sufficiently compact configuration to be located within theconfined region, orienting the housing so that the opening is adjacentthe target surface, and maintaining the housing substantially stationaryrelative to the target location while cycling curing radiation sourcealong the travel path within the housing.
 20. The method of claim 18,wherein the support is configured to maintain the housing stationaryduring cycling of the light source along the travel path.
 21. A workpiece comprising a cured coating according to the method of claim 17.22. A vehicle comprising a cured paint coating according to the methodof claim
 18. 23. A device for curing photoactivatable paint coatings,comprising: an undercarriage; a frame positioned on the undercarriage; ahousing supported on the frame, the housing having a back wall and aplurality of side wall portions extending therefrom to form a lightchamber, each side wall portion having a peripheral region terminatingat a UV light emission region; a UV light source contained within thelight chamber; a motorized carrier to support the UV light source in thelight chamber, the motorized carrier including a first travel cylinderconfigured to displace the UV light source along a travel path betweenopposed ends of the light chamber, and a second indexing cylinder tocause a synchronized incremental shift of the path so as to index and/oroscillate the UV light source along the travel path within the housing,and; a controller for controlling the motorized carrier withinboundaries; the boundaries of the travel path being identified by limitswitch units including a reversing unit for reversing the travel of thefirst travel cylinder following activation of a corresponding limitswitch unit; wherein the frame and undercarriage are further arranged tolocate the light chamber adjacent a target paint cure location on a workpiece, with the UV light emission region facing the paint cure location;and wherein the controller is operable to activate the UV light sourceand to initiate the motorized carrier to index and/or oscillate the UVlight source along the travel path to deliver UV light to the targetpaint cure location for curing UV curable paint thereon.
 24. The deviceof claim 23, wherein the light source is a fluorescent UV lamp emittingat a wavelength between about 200 to about 400 nanometers.
 25. Thedevice of claim 24, wherein the fluorescent UV lamp emits at awavelength between about 320 to about 390 nm.
 26. The device of claim25, wherein the UV light source includes one or more LED, fluorescentand/or incandescent lamps.